Manufacture of hcn



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ATTORNEYS Patented May 13, 1952 MANUFACTURE F HeN `Charles W. Perry, Bartlesville, Okla., assigner to Phillips PetroleumvCompanyz a corporation of l'Delaware ApplicationrJune 17, 1946, Serial No.,677,357

8'Clain`1s. 31

'This inventionrelates tothe'synthesis of .'hydrocyanic acid. One speci'c embodiment Yof the inventionpertains tothesynthesis'o'f HCN from NH3 and CO. `Another embodiment :relates to low molecular weighthydrocarbon.

"It is, an object ofthe invention to provide 'an improved continuous process "for manufacturing I-ICN.

.Another object` of `this invention is `tojjprovide Aan improved method of `supplying `heat for a continuous processfor 4synthesizing HCN.

A further object fof the invention' is 'to :provide a .process for producing HCN at highfconversion rates and relatively low cost. n p

VOther objectsof this inventioniwill ,become apparent 'from the accompanying disclosure.

Itlis 'found that HCN caribe producedrapdly inlarge yields atlow cost'by contacting a'stream `cfgas comprising NH3 `and either `CO Nor a low molecular Weighthydrooarbon with small, hot particles of 'heat transfer material which may be catalytic `or non-catalytic with `respectto the reaction.

In one embodiment of the invention, `pebbles of refractory "heattransfer material are` continuously flowed bygravity thru al series of zones, `ncludinga heating zoneVanda reactionzone, in .a 'uent mass and are simultaneously contacted in thei'heating zone with'astr'eam'ofhotggas and i in the reaction 'zonewith a stream-of the reactants. The `pebbles are heated to a .temperature `substantially above a predetermined reaction temperature and, as theyl pass 'thru the'reaction zone incontact with the reactants, 'thelatter are quicklyheatedto reaction temperatureand converted fto HCN. lThus the` hot `pebbles continuously entering Athe reaction ,zone are at 4a ,temperature'sufficient tosupply the heat required .to raise reactantfgases `to 4reaction temperature and also 'to supply'the heat required forthe reaction. Pebble 'temperatures "of 'at least"1'00o F. 'above .reaction temperature 'are yrequired Aand it is desirable at *times Vlto operate utilizing `pebble .inlet `temperatures of several :hundred degrees above reaction temperature. vDuring their passage thruthe reaction hamb'erfpebble `temperature drops several hundred lfdegrees 'and pebbles require retreating. Hence thepebbles are elevated by gas, bucket, Vorscrevvtypeelevator to Va chute'v above the `heating 'chamber and `are again allowed ,to jlow by *gravity thru theg'heating and reactionzones. `Pebbljediowisconveniently regulated bya star `feeder' locatedlfin the chute. leading ,from the outletfrom the Ylast ,pebble Chamber'to the elevator. Itis also feasible to regulate `pebble flow thru the "system by controlling the rate of `operation of the elevator.

The term .pebblemas used thruout this'speciiication denotes any refractorymaterialin uent formand `size which"willl.flow`readily by gravity thruthe various chambers of a pebble heater apparatus WithoutV entrainment in feedandA heating gases.`ilowing countercurrently. Pebbles are preferably substantially sphericalA and are about 1A," lto `1" in diameter with theV preferred range from 'about 4A" Ato 1/2'?. They `must 'be-rugged,

tough, andiresistantto'wear in order tofunction economically in pebble `heater operation.

For'straight thermal synthesisfpebbles 'of `rela.- tivelyrpure `alumina heattreated ^at extremely high temperatures to "render them substantially non-porous and glazed are most satisfactory. Pebbles of beryllia, Carborundum, mullite, vpericlase, andv zirconia, when properly lired, serve very well in the process of the invention. `Where a dual purpose pebble, providing `heat-'transfer and catalytic Yfunctions, 'is desirable, `pebbles of active alumina, alone,or impregnated r'With metal oxides of groups 3, 4, `5, and 6 of the Aperiodic table, are effective. Alumina having a minor amount of one Aor more ofthe oxidesof Th, Zr, Ce, V, and U incorporated therein is most desirable. Any of the conventional catalysts for `promoting the `reaction between NH3 andCO or hydrocarbons may Vbe incorporated in a refractory pebble, such as alumina, and lused in the process of the invention. Metals having la strong dehydrogenating effect, such as iron, should be avoided'since they'tend to cause complete `breakdown to'N, C, and H.

For a more :complete understanding 'of this lembodiment oftheyinvention reference `may be .hadtoFig 1 of .thedrawing which is 'adiag'ram- Vmatic showing of Ka 'pre'ferredarrangement of apparatus for performing the invention. lChambers II, I2, `and I3 are heat-insulated chambers inclosing a Afluent mass .of refractory `pebbles I0 andoonnected by .conduits I4 `andliwhlch form neck-likerpassageways between chambersland enclose (a portion of the fluent mass of pebbles. Conduite I6 and I1, connecting `chutes I8 and I9 respectively, with elevator .,2I, serve to convey pebbles lto heating l.chamber II and Afrom .prevheater I3, respectively. Elevator 2| Vmay be any type of conveyor such asagas lift, a screw, Vcr a bucket elevator, butthe last Lis preferred.

Iny Operation, gpebbles are continuously lLpassed into chute I8 `froinielevator 2| and descendsuc- "cessively thru inlet 'conduit I8, `"zh'arnber I I ,'.neck

I4, chamber I2, neck I5. chamber I3, outlet conduit II, chute I9 and star valve 22 (or other type of feeder) to elevator 2|. By proper control of star Valve 22, the rate of pebble flow thru the apparatus can be coordinated with flow of reactants and gas temperature in heater II to maintain the desired reaction temperature in reaction chamber I2. Increasing the iiow rate of pebbles increases the amount of heat available in reaction chamber I2 as does also an increase in pebble inlet temperature. Heat absorbed in reactor I2 depends upon the particular reactants and the temperature differential between reactant inlet temperature and effluent temperature. By controlling these variable factors, the reaction temperature may be carefully controlled.

Simultaneously with the flowing of pebbles thru the system just described, a countercurrent stream of hot gas, such as combustion gas, is continuously passed thru pebble heater II. Air and fuel gas are fed to furnace or burner 23 thru lines 24 and 25, respectively, and burned to produce the desired temperature in chamber Il. Combustion gas passing out of chamber II is conducted via line 26 thru heat-exchanger 21 which may conveniently preheat the air stream in line 24 where extremely high temperatures are desired. It is also desirable to recycle flue gas to pebble heating chamber II via line 2B controlled by valve 29. Likewise, fuel may be desirably preheated in heat-exchanger 3I in line 25. Lines 32 and 34 controlled by valves 33 and 35, respectively, are auxiliary air and fuel lines,

' respectively. In operating with catalytic pebbles it may be desirable to introduce other gases into the pebble heating zone in addition to hot combustion products in order to properly condition the catalyst. Steam or other treating gas may be introduced thru lines 24 and/ or 25. An excess of air over that required to oxidize the fuel may be introduced thru line 24 in order to burn off any carbon deposited on the pebbles in chamber I2 by cracking of hydrocarbons.

As hot pebbles flow thru reaction chamber I2, they are contacted by a countercurrent stream of reactants comprising NH3 and a suitable carbon-containing gas which reacts with the ammonia to form HCN. The feed gas is admitted thru line 35 controlled by valve 31 when operating at lower temperatures and/or when it is not desired to use chamber I3 for preheatng the feed and further reducing the temperature of the pebble stream for reasons discussed subsequently. As the feed gases pass thru reactor I2, they are quickly brought to reaction temperature and reaction takes place, absorbing heat from the pebble stream. In this manner the hotter pebbles supply heat for the endothermic reaction and the cooler pebbles heat up the feed to reaction temperature, thus providing highly efcient heating.

Reaction temperatures will Vary with the feed and the type of material in the pebbles. When operating with a feed comprising NH3 and CO and porous alumina pebbles, reaction temperatures can vary from about '750 to 1500D F., but a reaction temperature of about 900F. is preferred. The mol ratio of NH3 to CO in the feed may vary from about 1:25 to 120.5. When operating with NH3 and a light hydrocarbon as the feed, temperatures will vary with the type of hydrocarbon. Saturated hydrocarbons require considerably higher temperatures than the unsaturated and their reaction with NH3 is not influenced so much by catalysts. Temperatures of about 1800 F. are required to react saturated hydrocarbons with NH3 and reaction temperatures up to 2500 F. are desirable in catalytic conversion operations: When using relatively non-catalytic pebbles such as glazed, non-porous alumina, temperatures of about 2250 F. to 3000 F. are required for reaction of saturated hydrocarbons with NH3. Unsaturated hydrocarbons react with NH3 suitably in the presence of catalysts in the range of about 850 to 1650 F., while temperatures from about 1500 to 3000" F. are suitable in the absence of a catalyst. (With hydrocarbons in the feed, the mol ratio of N to C may desirably vary in the range of from about 1:5 to 1:0.3.) High temperatures and short reaction times when operating with hydrocarbons in the feed without the aid of strong catalysts are quite essential to good yields. Long heating periods at high temperatures promote decomposition of both the hydrocarbon and NH3, especially when'the hydrocarbon is saturated. Contact with metal surfaces likewise promotes complete decomposition of the reactants Yand lower yields. Pebble heater apparatus is ideally suited to production of HCN from NH3 and hydrocarbons because of the extremely'rapid heating and high temperatures obtainable in this typev of apparatus. Temperatures of upwards of 3000 F. and heating rates from 50 to 100 times faster than obtainable in ordinary tube reactors are obtainable in pebble heater apparatus.

Reaction time varies with the temperature when either `C0 or hydrocarbons are included in the feed stream, higher temperatures requiring shorter reactionV times. In the catalytic synthesis of HCN from NH3 and CO, reaction times of about 0.1 to 2 seconds are desirable under the practiced range of reaction conditions. When operating with hydrocarbons in the feed, reaction times may vary from about 0.01 to 1 second according to temperature, the particular hydrocarbon feed, and other variable reaction conditions, the shorter reaction times being desirable when operating at high temperatures.

It is usually advantageous to preheat the feed to within about to 1000 F. of thereaction Y temperature. When operating at 900 F. it is desirable to heat the feed to about '750 to 800 F., although heating to lower temperatures is also advantageous. In operating at temperatures of about 2500" to 3000 F., the feed should not be preheated much above 2000 F. since sharp heating from this temperature up produces greater yields of HCN and should be accomplished in the pebble heater reaction chamber.

When' -operating Vat the higher temperature levels, such as 1800 F. and up, itis particularly advantageous to pass the feed thru a preheating chamber .positioned in the line of pebble flow as I3 shown in Fig. 1. In such operation, pebbles leave chamber I2 at too high a temperature to be handled in ordinary elevator equipment; hence, passingfeed via line 38 thru chamber I3 in contact with the hot pebble stream I0 suitably preheats the feed and reduces the temperature of the pebbles sufficiently to allow the use of ordinary elevator equipment in transferringpebbles from chute I9 to chute I8. The preheated feed is passed via line 39, controlled by valve 4l, to feed line 3B. The feed stream may be split, a portion entering thru Valve 3,1 and the remainder thru .valve 4I, in order to provide flexible means of controlling. both feed and pebble-exit temperatures.

Eiiluents from reaction chamber I2 pass via line 42 `.thru .heat-transfer unit exchanger'` 3 I .to conventional ,product separationmeans 43 `where IICN is separated and recovered. Lines 44, 45,

46,-and 41 yare product take-off lines. Lines48 andt49 .controlled by valves 5I and 52, respectivelyrare provided forrecycling unreacted feed, H2, ethylene, and/or acetylene to feed line 138. In operating at higher temperatures it adds considerably to the yield of .HCN to quickly quench effluents. in .line 42 by means of a direct injection of cold fluid thru line 53 controlled by valve 54 thru automatic temperature controller-recorder 55 in accordance with .a predetermined downstream temperature. Quenching to temperatures at which-side reactions, polymerization, and decomposition cof products cease is preferred. Water, yethylene glycol, or any other non-deleterious fluid` may be used to advantage as quenching .materiaL .butof course, the vaporizing vof a liquid inthe eluent stream is the most eiicient quench. Knocking the eitluent stream down to 'about v600" F. *.is :usually sufficient, but in some cases .slightly lower and higher temperatures suilice. .The .eflluent stream then passes thru heat-exchanger 3 I in indirect heat-.exchange with the .Ifuel passing thru line and is desirably reduced to Aabout 150 to 300 F., beforebeing passed toseparation means 43.

Operation at `pressures varying only slightly either side of normal atmospheric pressure is conducive of good results, but pressures of about 0.5 `to `5 p. s. i. g. are preferred. Substantially lequal pressuresjn the pebble chambers aid in `preventinglow of `'gases from chamber to chamber. In some cases it may be desirable to operate with ia :non-deleterious blocking gas, such as steam, in necks I6, I4, I5, and I1 introduced thru lines 55, 51, 58, and 59, respectively. The same ordifferent igases may be used in these necks.

Figure L2 shows `a diagrammatic arrangement `of'apparatus forperforming another embodiment of the'invention in which solid, catalytic, heattransfermaterialin powdered form is passed successively thrua'heating zone and a reaction zone andthen back to the heating zone to repeat the cycle of conversion. Chamber I I incloses a powdered catalyst heating zone and chamber I2 incloses areaction zone. I-Iot iiue gas which may contain ra small percent of air is forced thru line GI "byblower 62, picks up powdered catalyst from-reactor I2 via line 63 controlled by valve 64, and 4carries itinto Vheater II. When operatingr under 'conditions'which cause carbon deposition on lthe catalyst particles, some heat is generated by 'burning off the carbon in heater II. Where insuiicient heat is generated'in this manner-to raise the'catalyst' temperature to the desired degree,additionalheat may be generated inheater I`I Iby introducinglhot ilue gas directly from furnace 23 4supplied lby `air vand fuel thru line 25. Fluegas passesout thru cyclone separator B5 and line`26 in whichis positioned precipitator 63 vfor removing `anynes notremoved by separator `65. TheLfnesffromseparator 65 drop backinto chamber LI I `and also .from Aprecipitator .6B .via .line `h1. Flueggas'maybe desirably recycled toline 6I via line 28 vcontrolled by Valve 29.

A desirableffeed gas is passed thru line 3.6 .by blower B8 and `picks up hot powdered catalyst from line 69 controlled by valve 1I as it comes from heater I I. The resulting vstream of `hot catalysteladen .reactants `.are passed into `reactor g I2 'atkhi'ghvelocity .andifurther reaction between the "feed .constituents takes place. Powdered catalystlggradually :drops .to thebottom of..reactor I2 andagain,passesinto'linel .via..line..33. .Hot veffluents .ffrom reactor .I2 .pass .via y.cyclone separator`12andi1ine 42 ,tofseparation means 43. `The temperature .of theeluents may be dropped quickly .to .the desired degree nby `injectidn into line `.42 .of `a .desirable quenching iluid via iline 53 and the temperature automatically controlled by temperature recorder-controller 55 in communication withline 42 and .valve54. Lines 44, 45, "46, and 41 are product take-oi`lines. Unreacted feed,"H2, ethylene and/or acetylene may be conveniently recycledlthru lines 48 and `4S! controlled by'valves .5 I `and .52.

The embodiment illustrated in Fig. 1 vhas a widerapplicationand is. more .suitable Vforhigher temperatures "than the embodiment.illustrated in Fig."'2. L'lfhelatterismore' advantageous in catalytic Qperation butmay alsobe used with pow- `dered,:non-"catalytic, `heat--transfer material.

Yields vary with temperatures, type of reastant, ratio of reactants, andreaction. time. Unsaturated hydrocarbons, such 'as C2H2, give greateryields"than" saturated hydrocarbons,. such as methane. `Operating with `a feed consisting of .NHsian'd C21-Irina ratio ofNto C of .1` to J2, a temperature of '2750 `F..and a reaction time `of v'0;06 second, a fyield `o'f'pver 9.0% v(based upon the ammonia converted to MHCN) is obtained. Under optimum'conditions with CH4 and NH3 as feedgyieldsnf morethan"`% (based upon `NH3 'convertedxtoHCm :are obtained. When `operating with VCO and NH3 as feed, yields on the same basis run ras high'as 80%.

It is believedthat high yields obtained when operating accordingto the invention are due to rapid heating of reactants, to .extremely high temperaturesand tothe prevention of contact .of reactants with vmetal reactor walls. When reacting 'NH3 and hydrocarbons in externally heated metal tubes none of these advantages is available. The processof the invention provides the further advantage of continuous production ofI-ICN at extremely high rates. Reconditioning of .heat-transfer elements, whether catalytic or relatively non-catalytic, continuously in heater `II prevents intermittent operation usually required l.tdrecondition the catalyst. This inven- .tion has a considerable advantage in economy as .welles inefficiency over processes requiring heating by electricity.

Various modifications of the inventionwill be apparentto those skilledin the art. Forexample, in operation with powdered catalystya plurality of :separators .may be advantageous where only one is shOWnLinFigure II :of the drawing.` The rillustrative details diselosedarenot to be construed as .imposing .unnecessary `limitations Von `the L invention.

I claim:

1. A continuous process for :manufacturing HCN which comprises continuously ilowing by gravity aA contiguous iiuent-masspfzhot l" to l yspherical refractory mon-catalytic pebbles thru a series of substantiallyverticallylarranged:zones comprisinga pebbleheating-zone and a reaction zone y positioned below 'said pebble heating `zone .and :communicating therewith `thru an unobstructed relatively narrow elongated zone, each lof 1saidzones being substantially lledwith said contiguous mass` of pebbles and permitting relatively .unrestricted flow of pebbles .therethru; regulatingftheflow of .pebbleszthrough saidgzones 4solely fa't;.a \point .downstreamfof the lowermost .of :saidtzones so .asfto .maintain afcornpactfand rhon- .tiguousstreamftofgpebbleszextending throuehfsaid zones;r continuously contacting that section of said contiguous mass of pebbles flowing thru said pebble heating zone with a stream of hot gas at a temperature and ow rate regulated to insure heating of said pebbles to a temperature substantially above a predetermined reaction temperature in the range of 1500 to 3000 F.; continuously contacting that section of said contiguous mass of pebbles flowing thru said reaction zone with a stream of reactant gases comprising NH3 and a carbon compound from the group consisting of CO and low molecular weight hydrocarbons at a gas-flow rate regulated to maintain said reactant gases at said predetermined reaction temperature solely by heat transfer from said pebbles whereby a substantial portion of said reactants are converted to HCN; continuously removing pebbles from the reaction zone; continuously introducing pebbles to said pebble heating zone; and recoveringl effluents from the reaction zone.

2. A continuous process for manufacturing HCN which comprises continuously ilowing by gravity a contiguous fluent mass of hot 1/3" to 1" spherical refractory non-catalytic pebbles thru a series of substantially vertically arranged zones comprising a pebble heating zone and a reaction zone positioned below said pebble heating zone and communicating therewith thru an unobstructed relatively narrow elongated zone, each of said zones being substantially filled with said contiguous mass of pebbles and permitting relatively unrestricted flow of pebbles therethru; regulating the flow of pebbles through said zones solely at a point downstream of the lowermost of said zones so as to maintain a compact and contiguous stream of pebbles extending through said zones; continuously contacting that section of said contiguous mass of pebbles flowing thru said pebble heating zone with a countercurrent stream of hot gas so as to heat same to a temperature above a predetermined reaction temperature in the range of 1500 to 3000 F.; continuously contacting that section of said contiguous mass of pebbles flowing thru said reaction zone with a preheated countercurrent stream of reactant gases comprising NH3 and a carboncontaining gas from the group consisting of CO and low molecular weight hydrocarbons; continuously quenching eiuents from the reaction zone; continuously removing pebbles from the lower portion of said reaction zone; continuously introducing pebbles to the upper portion of said pebble heating zone; simultaneously controlling and correlating the temperature of said hot gas, the rate of pebble flow, and the rate of flow of said stream of reactant gases so as to maintain said predetermined reaction temperature solely by heat transfer from said pebbles, whereby a substantial portion of said reactants are converted to HCN; and recovering HCN.

3. The process of claim 2 in which the reactant gases comprises NH3 and CO in a ratio of between about 1125 and 110.5.

4. The process of claim 2 in which the reactant gases comprise NH3 and a low molecular weight hydrocarbon in aratio of N to C of between about 1:5 and 110.3.

5. A continuous process for manufacturing HCN which comprises continuously flowing by gravity a contiguous fluent mass of hot pebbles consisting of non-catalytic alumina spheres 1/8" to 1" in diameter thru a series of substantially vertically arranged zones comprising a pebble heating zone, and a reaction zone positioned below said pebble heating zone and communicating therewith thruV an unobstructed relatively narrow elongated zone, each of said zones being substantially lled with said contiguous mass of pebbles and permitting relatively unrestricted flow of pebbles therethru; regulating the flow of pebbles through said zones solely at a point downstream of the lowermost of said zones so as to maintain a compact and contiguous stream of pebbles extending through said zones; continuously contacting that section of said contiguous mass of pebbles flowing thru said pebble heating zone with a countercurrent stream of hot'gas; continuously contacting that section of said contiguous mass of pebbles flowing thru said reaction zone `with a preheated countercurrent stream of reactant gases comprising NH3 and CO in a ratio of between about 1:25 and 110.5; continuously quenching eiiluents from the reaction zone; continuously removing pebbles'from the lower portion of said reaction zone; continuously introducing pebbles to the upper portion or said pebble heating zone; simultaneously 'controlling and correlating the temperature of said hot'gas, the rate of pebble flow, andthe rate of low ofY said stream of reactant gases so as to maintain a predetermined reactiontemperature within the range of 1500 F. to 3000 F., solely by heat transfer from said pebbles, whereby a substantial portion of said reactants are converted to HCN; and recovering HCN.

6. A continuous process for manufacturing I-ICN which comprises continuously owing by gravity a contiguous fluent mass of hot pebbles consisting of non-catalytic, glazed alumina spheres l" to 1" in diameter thru a series of substantially vertically arranged zones comprising a pebble heating zone and a reaction zone positioned below said pebble heating zone and communicating therewith thru an unobstructed relatively narrow elongated zone, each of said zones being substantially filled With said contiguous mass of pebbles and permitting relatively unrestricted flow of pebbles therethru; regulating the flow of pebbles through said zones solely at a point downstream of the lowermost ofrsaid zones so as to maintain a compact and contiguous stream'of pebbles extending through said zones; continuously contacting that section of said contiguous mass of pebbles flowing thru said pebble heating zone with a countercurrent stream of hot gas; continuously contacting that section of said contiguous mass of pebbles iiowing thru said reaction zone with a preheated countercurrent stream of reactant gases comprising NH3 and an unsaturated low molecular weight hydrocarbon; continuously quenching effluents from the reaction zone; continuously removing pebbles from the lower portion of said reaction zone; continuously introducing pebbles to the upper portion of said pebble heating zone; simultaneously controllingand correlating the temperature of said hot gas, the rate of pebble ow, and the rate of flow of said stream of reactant gases so as to maintain a predetermined reaction temperature within the range of 1500 to 3000 F. solely by heat transfer from said pebbles, whereby a substantial portion of said reactants are converted to HCN; and recovering HCN.

7. A continuous process for manufacturing HCN which comprises continuously ilowing by gravity a contiguous iluent mass of hot pebbles consisting of non-catalytic, glazed valumina spheres M3" to 1" in diameter thru a series of substantially vertically arranged zones comprising a pebble heating zone and a reaction zone positioned below said pebble heating zone and communicating therewith thru an unobstructed relatively narrow elongated zone, each of said zones being substantially nlled with said contiguous mass of pebbles and permitting relatively unrestricted flow of pebbles therethru; regulating the ow of pebbles through said zones solely at a point downstream of the lowermost of said zones so as to maintain a compact and contiguous stream of pebbles extending through said zones; continuously contacting that section of said contiguous mass of pebbles flowing thru said pebble heating zone with a countercurrent stream of hot gas; continuously contacting that section of said contiguous mass of pebbles flowing thru said reaction zone with a preheated countercurrent stream of reactant gases comprising NH3 and C2H2; continuously quenching eiiluents from the reaction zone; continuously removing pebbles from the lower portion of said reaction zone; continuously introducing pebbles to the upper portion of said pebble heating zone; simultaneously controlling and correlating the temperature of said hot gas, the rate of pebble flow, and the rate of flow of said stream of reactant gases so as to maintain a predetermined reaction temperature within the range of 1500 to 3000 F. solely by heat transfer from said pebbles, whereby a substantial portion of said reactants are con verted to I-IC'N; and recovering HCN.

8. A continuous process for manufacturing HCN which comprises continuously flowing by gravity a contiguous fluent mass of hot pebbles consisting of non-catalytic glazed alumina spheres 1/8" to 1 in diameter thru a series of substantially vertically arranged zones comprising a pebble heating zone and a reaction zone positioned below said pebble heating zone and communicating therewith thru an unobstructed relatively narrow elongated zone, each of said zones being substantially lled with said contiguous mass of pebbles and permitting relatively unrestricted flow of pebbles therethru; regulating the now of pebbles through said zones' solely at a point downstream of the lowermost of said zones so as to maintain a compact and contiguous stream of pebbles extending through said zones; continuously contacting that section of said contiguous mass of pebbles flowing thru said pebble heating zone with a countercurrent stream of hot gas; continuously contacting that section of said contiguous mass of pebbles iiowing thru said reaction zone with a preheated countercurrent stream of reactant gases comprising NI-I and CH/l; continuously quenching eliuents from the reaction zone; continuously removing pebbles from the lower portion of said reaction zone; continuousiy introducing pebbles to the upper portion of said pebble heating zone; simultaneously controlling and correlating the temperature oi said hot gas, the rate of pebble now, and the rate of flow of said stream of reactant gases so as to maintain a predetermined reaction temperature within the range of 1800" to 3000 F. solely by heat transfer from said pebbles, whereby a substantial portion of said reactants are converted to HCN; and recovering HCN.

CHARLES W. PERRY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,610,035 Bredig et al Dec. 7, 1926 1,982,407 Wheeler Nov. 27, 1934 2,069,545 Carlisle et al Feb. 2, 1937 2,387,378 Wolk Oct. 23, 1945 2,389,636 Ramseyer Nov. 27, 1945 2,477,042 Burnside July 26, 1949 

1. A CONTINUOUS PROCESS FOR MANUFACTURING HCN WHICH COMPRISES CONTINUOUSLY FLOWING BY GRAVITY A CONTIGUOUS FLUENT MASS OF HOT 1/8" TO 1" SPHERICAL REFRACTORY NON-CATALYTIC PEBBLES THRU A SERIES OF SUBSTANTIALLY VERTICALLY ARRANGED ZONES COMPRISING A PEBBLE HEATING ZONE AND A REACTION ZONE POSITIONED, BELOW SAID PEBBLE HEATING ZONE AND COMMUNICATING THEREWITH THRU AN UNOBSTRUCTED RELATIVELY NARROW ELONGATED ZONE, EACH OF SAID ZONES BEING SUBSTANTIALLY FILLED WITH SAID CONTIGUOUS MASS OF PEBBLES AND PERMITTING RELATIVELY UNRESTRICTED FLOW OF PEBBLES THERETHRU; REGULATING THE FLOW OF PEBBLES THROUGH SAID ZONES SOLELY AT A POINT DOWNSTREAM OF THE LOWERMOST OF SAID ZONES SO AS TO MAINTAIN A COMPACT AND CONTIGUOUS STREAM OF PEBBLES EXTENDING THROUGH SAID ZONES; CONTINUOUSLY CONTACTING THAT SECTION OF SAID CONTIGUOUS MASS OF PEBBLES FLOWING THRU SAID PEBBLE HEATING ZONE WITH A STREAM OF HOT GAS AT A TEMPERATURE AND FLOW RATE REGULATED TO INSURE HEATING OF SAID PEBBLES TO A TEMPERATURE SUBSTANTIALLY ABOVE A PREDETERMINED REACTION TEMPERATURE IN THE RANGE OF 1500* TO 3000* F.; CONTINUOUSLY CONTACTING THAT SECTION FO SAID CONTIGUOUS MASS OF PEBBLES FLOWING THRU SAID REACTION ZONE WITH A STREAM OF REACTANT GASES COMPRISING NH3 AND A CARBON COMPOUND FROM THE GROUP CONSISTING OF CO AND LOW MOLECULAR WEIGHT HYDROCARBONS AT A GAS-FLOW RATE REGULATED TO MAINTAIN SAID REACTANT GASES AT SAID PREDETERMINED REACTION TEMPERATURE SOLELY BY HEAT TRANSFER FROM SAID PEBBLES WHEREBY A SUBSTANTIAL PORTION OF SAID REACTANTS ARE CONVERTED TO HCN; CONTINUOUSLY REMOVING PEBBLES FROM THE REACTION ZONE; CONTINUOUSLY INTRODUCING PEBBLES TO SAID PEBBLE HEATING ZONE; AND RECOVERING EFFLUENTS FROM THE REACTION ZONE. 